The invention relates to improvements in methods of and in apparatus for classifying and/or otherwise treating rubble, such as building rubble. More particularly, the invention relates to improvements in methods of the type described on pages 443, 446 and 447 of German-language publication entitled "AUFBEREITUNGSTECHNIK" (No. 8, 1987) and to improvements in apparatus of the type disclosed in German patent application No. 21 61 310 Eder (published Jun. 29, 1972).
Treatment (particularly cleaning) of rubble presents many problems, especially in the building industries. For example, sand which is obtained from building rubble is often unsuitable for utilization in connection with the making of concrete because individual sand particles in the form of granules, kernels or the like are frequently coated with films of contaminants consisting of fine dust or the like. Such contaminants prevent proper bonding of particles of sand in concrete. Serious problems are encountered in connection with further processing of building rubble regardless of the origin of such material, e.g., as a result of demolition of buildings and/or as a result of comminution of pieces of rock, stone or the like. Furthermore, the thus Obtained coarser and/or finer particles of sand cannot always be deposited at regular dumping grounds because many federal and/or regional authorities enforce strict rules pertaining to the degree of permissible contamination of sand which is to be deposited on such dumping grounds. Therefore, the materials must be subjected to an expensive cleaning or decontaminating treatment prior to being discharged at standard or regular dumping grounds, or they must be transported to specially designated dumping facilities. All this involves the expenditure of substantial sums of money. In addition, the materials are wasted, i.e., they are not recycled for renewed use in the building and/or related industries. Still further, it is desirable to avoid the deposition of large quantities of potentially reusable materials at special dumping facilities in order to avoid rapid saturation of such facilities and the need for establishment of fresh facilities for disposal of certain types of bulky materials such as building rubble. As a rule, building rubble will contain various chemicals, which are classified as contaminants, as well as fragments of wood and other natural substances.
In accordance with heretofore known proposals, cleaning of building rubble involves segregation of large and medium-sized sand particles from small and very small particles. Such segregation is carried out in water which continues to contain small and very small particles of sand as well as certain other contaminants (particularly heavy metals, polyaromatic substances and/or others) when the step of segregating large and medium large sand particles is completed. Turbid water which contains heavy metals, polyaromatic substances and/or other contaminants and small and very small particles of sand is thereupon treated to separate the solid and liquid fractions. The thus segregated solid matter must be delivered to and disposed at special dumping facilities. The presence of fine sand particles contributes to the bulk of material which must be disposed of at special dumping facilities and, furthermore, such fine particles of sand are wasted, i.e., they are not reused in the building and/or other industries.
Apparatus which are used to relieve water of minute particles of sand and/or other contaminants subsequent to recovery of large and medium-sized sand particles normally employ vessels with laminations which are completely immersed in the body of liquid (normally water) to be treated. The solid particles are supposed to settle at the bottom of the vessel and are removed at intervals. Each such removal involves the development of a pressure shock or thrust which propagates itself through the entire vessel and creates turbulence which affects the quality and prolongs the duration of segregation of solid particles. The shocks or thrusts are sufficiently pronounced to exert a pronounced adverse influence upon the water purifying treatment. Thus, the shocks affect the segregation of particles which are to rise to the surface o the body of water in the vessel as well as the segregation of particles which are supposed to descend into the bottom portion of the vessel. Consequently, solids which are removed from the surface as well as from the bottom zone of the vessel contain a very high percentage of water. This is undesirable irrespective of whether the thus separated solid materials are to be recycled or dumped at special dumping facilities. Water which is contained in the materials to be dumped adds to the overall weight of the materials to be disposed of. On the other hand, any percentage of water (or an excessive percentage of water) in a mass of segregated solid material which is to be recycled (e.g., in the building industry) must be segregated from the solid fraction in an additional step which contributes to the already high cost of a conventional recycling operation.